Sealing device

Abstract

A sealing device particularly suitable for sealing pistons of working cylinders and for sealing two machine components which can slide against one another is disclosed. A conventional sealing element consisting of low-friction, but not very elastic material, such as PTFE plastic material, and resting on an elastic support, is used. The cross-section of the sealing element in a direction of the sliding motion is U-shaped and encircles the support. The dimensions of the support and the sealing element are determined such that the support exerts prestress forces on the sealing element which try to bend the rim areas of the sealing element outward against the sliding surface for the sealing element. Consequently, an additional force component, directed toward the sliding surface, results for the pressure force which is exerted on the sealing element by the support and functions as a sealing force.

We claim: 
     
       1. A sealing apparatus for sealing two longitudinal extending machine components which can slide relative to and against one another longitudinally, a first of such two machine components having a sliding surface along which a second of such two machine components slides longitudinally to define a sliding motion, said sealing apparatus comprising: (a) a plastic sealing element having low friction and relatively low elasticity secured to said second machine component;   (b) an elastic support member positioned intermediate said plastic sealing element and said second machine component to exert a force on at least a portion of said plastic sealing element which slides along said sliding surface of said first machine component and to provide support for said plastic sealing element, said elastic support member having an elasticity in cross-section at least in a plane perpendicular to said sliding surface on said first machine component;   (c) at least a portion of said plastic sealing element which slides along said sliding surface on said first machine component encircles said elastic support member in a direction of said sliding motion;   (d) mounting protrusions integral with and extending from said plastic sealing element and extending in cross-section in a plane substantially perpendicular to said sliding surface on said first machine component to engage corresponding support surfaces of said elastic support member, said corresponding support surfaces are oriented in cross-section in a plane substantially perpendicular to said mounting protrusions;   (e) an outer dimension of said corresponding support surfaces, measured in a direction of said sliding motion, is greater than a distance between said mounting protrusions of said plastic sealing element when said plastic sealing element and said elastic support member are in an unmounted condition;   (f) said portion of said plastic sealing element, which slides along said sliding surface on said first machine component, includes a predetermined prestress exerted by said corresponding support surfaces on said mounting protrusions in the direction of said sliding motion of said sliding surface, on said first machine component at least in an area of said mounting protrusions; and   (g) said elastic support member includes sleeve-shaped protrusions extending substantially in said direction of said sliding motion and carrying said plastic sealing element and an end of each sleeve-shaped protrusion forming a respective support surface of said elastic support member and said elastic suppport member further includes a means positioned to engage adjacent each end of said sleeve-shaped protrusions and said second machine component for providing elastic cushioning for said sleeve-shaped protrusions.   
     
     
       2. A sealing apparatus, according to claim 1, wherein said at least one sleeve-shaped protrusion of said elastic support member is formed from a relatively elastic material. 
     
     
       3. A sealing apparatus, according to claim 2, wherein said relatively elastic material is rubber. 
     
     
       4. A sealing apparatus, according to claim 3, wherein in a plane perpendicular to said sliding surface on said first machine component and in said direction of said sliding motion a cross-section of said elastic support member is T-shaped and each end of a portion representing a crossbar of said T form support surfaces of said elastic support member. 
     
     
       5. A sealing apparatus, according to claim 2, wherein in a plane perpendicular to said sliding surface on said first machine component and in said direction of said sliding motion a cross-section of said elastic support member is T-shaped and each end of a portion representing a crossbar of said T form support surfaces of said elastic support member. 
     
     
       6. A sealing apparatus, according to claim 1, wherein in a plane perpendicular to said sliding surface on said first machine component and in said direction of said sliding motion a cross-section of said elastic support member is T-shaped and each end of a portion representing a crossbar of said T form support surfaces of said elastic support member. 
     
     
       7. A sealing apparatus for sealing two longitudinal extending machine components which can slide relative to and against one another longitudinally, a first of such two machine components having a sliding surface along which a second of such two machine components slides longitudinally to define a sliding motion, said sealing apparatus comprising: (a) a plastic sealing element having low friction and relatively low elasticity secured to said second machine component;   (b) an elastic support member positioned intermediate said plastic sealing element and said second machine component to exert a force on at least a portion of said plastic sealing element which slides along said sliding surface of said first machine component and to provide support for said plastic sealing element, said elastic support member having an elasticity in cross-section at least in a plane perpendicular to said sliding surface on said first machine component;   (c) at least a portion of said plastic sealing element which slides along said sliding surface on said first machine component encircles said elastic support member in a direction of said sliding motion;   (d) mounting protrusions integral with and extending in cross-section from said plastic sealing element and extending in a plane substantially perpendicular to said sliding surface on said first machine component to engage corresponding support surfaces of said elastic support member, said corresponding support surfaces are oriented in cross-section in a plane substantially perpendicular to said mounting protrusions;   (e) an outer dimension of said corresponding support surfaces, measured in a direction of said sliding motion, is greater than a distance between said mounting protrusions of said plastic sealing element when said plastic sealing element and said elastic support member are in an unmounted condition;   (f) said portion of said plastic sealing element, which slides along said sliding surface on said first machine component, includes a predetermined prestress exerted by said corresponding support surfaces on said mounting protrusions in the direction of said sliding motion of said sliding surface on said first machine component at least in an area of said mounting protrusions;   (g) said two machine components form a working cylinder, and said first of said two machine components is a cylinder, and said second of said two machine components is a piston carrying said elastic support member, and said portion of said plastic sealing element which slides along said sliding surface of said cylinder is part of a packing assembly secured to said piston; and   (h) said elastic support member includes sleeve-shaped protrusions extending substantially in said direction of said sliding motion and carrying said plastic sealing element and an end of each sleeve-shaped protrusion forming a respective support surface of said elastic support member and said elastic support member further includes a means positioned to engage adjacent each end of said sleeve-shaped protrusions and said second machine component for providing elastic cushioning for said sleeve-shaped protrusions.   
     
     
       8. A sealing apparatus, according to claim 2, wherein in a plane perpendicular to said sliding surface on said first machine component and in said direction of said sliding motion a cross-section of said elastic support member is T-shaped and each end of a portion representing a crossbar of said T form support surfaces of said elastic support member. 
     
     
       9. A sealing apparatus, according to claim 8, wherein said at least one sleeve-shaped protrusion of said elastic support member is formed from a relatively elastic material. 
     
     
       10. A sealing apparatus, according to claim 9, wherein said relatively elastic material is rubber. 
     
     
       11. A sealing apparatus, according to claim 9, wherein in a plane vertical to said sliding surface on said first machine component and in said direction of said sliding motion a cross-section of said elastic support member is T-shaped and each end of a portion representing a crossbar of said T form support surfaces of said elastic support member. 
     
     
       12. A sealing apparatus, according to claim 7, wherein said sealing apparatus further includes: (a) two rigid support elements secured to said piston to support end portions of said elastic support member having said support surfaces; and   (b) elastic support members positioned between said rigid support elements and said end portions of said elastic support member.   
     
     
       13. A sealing apparatus, according to claim 12, wherein said elastic support members are formed as rings. 
     
     
       14. A sealing apparatus, according to claim 13, wherein said rings are O-rings. 
     
     
       15. A sealing apparatus for sealing two longitudinal extending machine components which can slide relative to and against one another longitudinally, a first of such two machine components having a sliding surface along which a second of such two machine components slides longitudinally to define a sliding motion, said sealing apparatus comprising: (a) a plastic sealing element having low friction and relatively low elasticity secured to said second machine component;   (b) an elastic support member positioned intermediate said plastic sealing element and said second machine component to exert a force on at least a portion of said plastic sealing element which slides along said sliding surface of said first machine component and to provide support for said plastic sealing element, said elastic support member having an elasticity in cross-section at least in a plane perpendicular to said sliding surface on said first machine component;   (c) at least a portion of said plastic sealing element which slides along said sliding surface on said first machine component encircles said elastic support member in a direction of said sliding motion;   (d) mounting protrusions integral with and extending from said plastic sealing element and extending in cross-section in a plane substantially perpendicular to said sliding surface on said first machine component to engage corresponding support surfaces of said elastic support member, said corresponding support surfaces are oriented in cross-section in a plane substantially perpendicular to said mounting protrusions;   (e) an outer dimension of said corresponding support surfaces, measured in a direction of said sliding motion, is greater than a distance between said mounting protrusions of said plastic sealing element when said plastic sealing element and said elastic support member are in an unmounted condition;   (f) said portion of said plastic sealing element, which slides along said sliding surface on said first machine component, includes a predetermined prestress exerted by said corresponding support surfaces on said mounting protrusions in the direction of said sliding motion of said sliding surface on said first machine component at least in an area of said mounting protrusions;   (g) in a plane perpendicular to said sliding surface on said first machine component and in said direction of said sliding motion a cross-section of said plastic sealing element is U-shaped and two side portions of said U-shaped plastic sealing element form said mounting protrusions; and   (h) said elastic support member includes sleeve-shaped protrusions extending substantially in said direction of said sliding motion and carrying said plastic sealing element and an end of each sleeve-shaped protrusion forming a respective support surface of said elastic support member and said elastic suppport member further includes a means positioned to engage adjacent each end of said sleeve-shaped protrusions and said second machine component for providing elastic cushioning for said sleeve-shaped protrusions.   
     
     
       16. A sealing apparatus, according to claim 15, wherein said at least one sleeve-shaped protrusion of said elastic support member is formed from a relatively elastic material. 
     
     
       17. A sealing apparatus, according to claim 16, wherein in a plane perpendicular to said sliding surface on said first machine component and in said direction of said sliding motion a cross-section of said elastic support member is T-shaped and each end of a portion representing a crossbar of said T form support surfaces of said elastic support member. 
     
     
       18. A sealing apparatus, according to claim 16, wherein said relatively elastic material is rubber. 
     
     
       19. A sealing apparatus, according to claim 15, wherein in a plane perpendicular to said sliding surface on said first machine component and in said direction of said sliding motion a cross-section of said elastic support member is T-shaped and each end of a portion representing a crossbar of said T form support surfaces of said elastic support member. 
     
     
       20. A sealing apparatus for sealing two longitudinal extending machine components which can slide relative to and against one another longitudinally, a first of such two machine components having a sliding surface along which a second of such two machine components slides longitudinally to define a sliding motion, said sealing apparatus comprising: (a) a plastic sealing element having low friction and relatively low elasticity secured to said second machine component;   (b) an elastic support member positioned intermediate said plastic sealing element and said second machine component to exert a force on at least a portion of said plastic sealing element which slides along said sliding surface of said first machine component and to provide support for said plastic sealing element, said elastic support member having an elasticity in cross-section at least in a plane perpendicular to said sliding surface on said first machine component;   (c) at least a portion of said plastic sealing element which slides along said sliding surface on said first machine component encircles said elastic support member in a direction of said sliding motion;   (d) mounting protrusions integral with and extending from said plastic sealing element and extending in cross-section in a plane substantially perpendicular to said sliding surface on said first machine component to engage corresponding support surfaces of said elastic support member, said corresponding support surfaces are oriented in cross-section in a plane substantially perpendicular to said mounting protrusions;   (e) an outer dimension of said corresponding support surfaces, measured in a direction of said sliding motion, is greater than a distance between said mounting protrusions of said plastic sealing element when said plastic sealing element and said elastic support member are in an unmounted condition;   (f) said portion of said plastic sealing element, which slides along said sliding surface on said first machine component, includes a predetermined prestress exerted by said corresponding support surfaces on said mounting protrusions in the direction of said sliding motion of said sliding surface on said first machine component at least in an area of said mounting protrusions;   (g) said two machine components form a working cylinder, and said first of said two machine components is a cylinder, and said second of said two machine components is a piston carrying said elastic support member, and said portion of said plastic sealing element which slides along said sliding surface of said cylinder is part of a packing assembly secured to said piston;   (h) in a plane perpendicular to said sliding surface on said first machine component and in said direction of said sliding motion a cross-section of said plastic sealing element is U-shaped and two side portions of said U-shaped plastic sealing element form said mounting protrusions; and   (i) said elastic support member includes sleeve-shaped protrusions extending substantially in said direction of said sliding motion and carrying said plastic sealing element and an end of each sleeve-shaped protrusion forming a respective support surface of said elastic support member and said elastic suppport member further includes a means positioned to engage adjacent each end of said sleeve-shaped protrusions and said second machine component for providing elastic cushioning for said sleeve-shaped protrusions.   
     
     
       21. A sealing apparatus, according to claim 20, wherein said at least one sleeve-shaped protrusion of said elastic support member is formed from a relatively elastic material. 
     
     
       22. A sealing apparatus, according to claim 21, wherein said relatively elastic material is rubber. 
     
     
       23. A sealing apparatus, according to claim 21, wherein in a plane perpendicular to said sliding surface on said first machine component and in said direction of said sliding motion a cross-section of said elastic support member is T-shaped and each end of a portion representing a crossbar of said T form support surfaces of said elastic support member. 
     
     
       24. A sealing apparatus, according to claim 20, wherein in a plane perpendicular to said sliding surface on said first machine component and in said direction of said sliding motion a cross-section of said elastic support member is T-shaped and each end of a portion representing a crossbar of said T form support surfaces of said elastic support member.